Object detection system, object detection method, and non-transitory computer-readable medium storing object detection program

Abstract

An object detection system includes a reader waveguide ( 101 ) formed as an open transmission line, an RFID tag ( 102 ) placed above the reader waveguide ( 101 ), a signal strength acquisition unit ( 103 ) that acquires signal strength of a read signal read from the RFID tag ( 102 ) by electromagnetic coupling through the reader waveguide ( 101 ), and an object detection unit ( 104 ) that detects physical characteristics of an object ( 105 ) corresponding to the acquired signal strength based on a relationship between a plurality of (three or more values of) signal strength of the read signal and physical characteristics of the object to be detected.

The invention claimed is: 
     
       1. An object detection system comprising:
 a reader waveguide formed as an open transmission line; 
 an RFID tag placed above the reader waveguide, the RFID tag being placed in such a manner that a positional relationship between the RFID tag and the reader waveguide is predetermined regardless of a presence or an absence of an object; 
 a signal strength acquisition unit that acquires signal strength of a read signal read from the RFID tag by electromagnetic coupling through the reader waveguide; and 
 an object detection unit that detects physical characteristics of the object corresponding to the acquired signal strength based on a relationship between three or more values of signal strength of the read signal and physical characteristics of the object to be detected. 
 
     
     
       2. The object detection system according to  claim 1 , wherein the physical characteristics include any one of a position, a size, a material and a shape of the object. 
     
     
       3. The object detection system according to  claim 1 , wherein the object detection unit detects the physical characteristics of the object based on a variation in signal strength of the read signal. 
     
     
       4. The object detection system according to  claim 1 , wherein the object detection unit detects the physical characteristics of the object corresponding to the acquired signal strength based on a relational expression representing a relationship between the signal strength of the read signal and the physical characteristics of the object. 
     
     
       5. The object detection system according to  claim 4 , wherein
 the relational expression includes a plurality of parameters related to the physical characteristics of the object, and 
 the object detection unit detects the physical characteristics of the object by using the relational expression where a parameter of the plurality of parameters is set as a condition for detection. 
 
     
     
       6. The object detection system according to  claim 5 , wherein the plurality of parameters include a characteristic parameter indicating the physical characteristics of the object and a position parameter indicating a position of the object. 
     
     
       7. The object detection system according to  claim 6 , wherein the characteristic parameter includes any one of a size, a material and a shape of the object. 
     
     
       8. The object detection system according to  claim 6 , wherein the position parameter includes a position of the object in a horizontal direction relative to the RFID tag and a position of the object in a vertical direction relative to the RFID tag. 
     
     
       9. The object detection system according to  claim 1 , wherein
 a plurality of RFID tags are placed above the reader waveguide, and 
 the object detection unit detects the physical characteristics of the object based on signal strength of the read signal read from a first RFID tag and a second RFID tag among the plurality of RFID tags. 
 
     
     
       10. The object detection system according to  claim 9 , wherein the object detection unit calculates one of an average value and a weighted average value of the physical characteristics of the object detected based on signal strength of the read signal read from the first RFID tag and the physical characteristics of the object detected based on signal strength of the read signal read from the second RFID tag. 
     
     
       11. The object detection system according to  claim 9 , wherein, when the first RFID tag and the second RFID tag are placed adjacent to each other, and signal strength of the read signal read from the first RFID tag and signal strength of the read signal read from the second RFID tag satisfy a specified condition, the object detection unit detects the physical characteristics of the object in an area between the first RFID tag and the second RFID tag. 
     
     
       12. The object detection system according to  claim 9 , wherein, when the first RFID tag is placed between a third RFID tag and the second RFID tag among the plurality of RFID tags, and signal strength of the read signal read from the first RFID tag satisfies a specified condition, the object detection unit detects the physical characteristics of the object in one of an area between the first RFID tag and the second RFID tag and an area between the first RFID tag and the third RFID tag. 
     
     
       13. The object detection system according to  claim 12 , wherein the object detection unit detects the physical characteristics of the object in an area between the first RFID tag and one of the second RFID tag and the third RFID tag with higher signal strength of the read signal. 
     
     
       14. The object detection system according to  claim 9 , wherein, when the first RFID tag is placed at an end of a line of the plurality of RFID tags, the first RFID tag and the second RFID tag are placed adjacent to each other, and signal strength of the read signal read from the first RFID tag satisfies a specified condition, the object detection unit detects the physical characteristics of the object in one of an area between the first RFID tag and the second RFID tag and an area on a side where the second RFID tag is not placed. 
     
     
       15. The object detection system according to  claim 1 , wherein
 a plurality of RFID tags are placed above the reader waveguide, and 
 the object detection unit makes a determination about an overlap state where the object overlaps on the plurality of RFID tags according to signal strength of the read signal, and detects a shape of the object based on the overlap state. 
 
     
     
       16. The object detection system according to  claim 1 , wherein
 a plurality of RFID tags are placed above the reader waveguide, 
 the object detection system further includes an isoline calculation unit that calculates an isoline based on signal strength of the read signal read from the plurality of RFID tags, and 
 the object detection unit detects a shape of the object based on the calculated isoline. 
 
     
     
       17. An object detection method comprising:
 acquiring signal strength of a read signal read from an RFID tag placed above a reader waveguide formed as an open transmission line by electromagnetic coupling through the reader waveguide, the RFID tag being placed in such a manner that a positional relationship between the RFID tag and the reader waveguide is predetermined regardless of a presence or an absence of an object; and 
 detecting physical characteristics of the object corresponding to the acquired signal strength based on a relationship between three or more values of signal strength of the read signal and physical characteristics of the object to be detected. 
 
     
     
       18. A non-transitory computer-readable medium storing an object detection program causing a computer to execute an object detection process, the object detection process comprising:
 acquiring signal strength of a read signal read from an RFID tag placed above a reader waveguide formed as an open transmission line by electromagnetic coupling through the reader waveguide, the RFID tag being placed in such a manner that a positional relationship between the RFID tag and the reader waveguide is predetermined regardless of a presence or an absence of an object; and 
 detecting physical characteristics of the object corresponding to the acquired signal strength based on a relationship between three or more values of signal strength of the read signal and physical characteristics of the object to be detected. 
 
     
     
       19. An object detection system comprising:
 a reader waveguide formed as an open transmission line; 
 an RFID tag placed above the reader waveguide, the RFID tag being placed in such a manner that a positional relationship between the RFID tag and the reader waveguide is predetermined regardless of a presence or an absence of an object; 
 a signal strength acquisition means for acquiring signal strength of a read signal read from the RFID tag by electromagnetic coupling through the reader waveguide; and 
 an object detection means for detecting physical characteristics of the object corresponding to the acquired signal strength based on a relationship between three or more values of signal strength of the read signal and physical characteristics of the object to be detected.